Lock for hydraulic piston



- April 95 V M. E. PAPANQ'LI 2,787,252

LOCK FOR HYDRAULIC PISTON Filed June 24, 1955 2 Sheets-Sheet 1 April 2, 1957 M. EJPAPANOLI 2,787,252

LOCK FOR HYDRAULIC PISTON Filed June 24, 1955 2 Sheets-Sheet 2 LOCK FOR HYDRAULIC. PISTQN Michael E. Papanoli, Spring Lake, Mich.,.assignor to The Chailenge Machinery Company,'Grand Haven, Mrcln, a corporation of Michigan Application June-24, 1955, Serial No. 517,681

2 Claims. (Cl. 121-40) This invention relates to alockforapressure operated piston. It is for the purpose of automatically locking the piston in its extended position so that it willremain in that position for. a long time after. the pressure behind it has been reduced or, in fact, completely removed;

Although this device may be, adopted for other uses, it is particularly intended for hydraulically operated paper cutters. Such a paper cutter has a very sharp knife attached to a knife bar, the combined weight of which is considerable. The knife and bar are vertically reciprocated by a hydraulic piston in a cylinder. The knife is forced downwardly .for. the :cutting stroke and is lifted to raised position by the-1 piston.

The raised position is normal in which the knife is at rest and itqremains for. long periods such. as over night or for longer times when the machine is not being used.

In present practice the knife and. knife bar are held in raised position entirely by the pressure of the fluid in the cylinder beneath the piston. But because of ordinary defects in the pressure system, such as leaking valves or piston packing, the pressure will not hold for long periods when the machine is idle. When in raised position the sharp edge of the knife is guarded by a pressure bar but when the pressure below the piston diminishes, the knife will lower so that its edge is exposed which may cause serious injury to the hands of an operator.

The present invention provides a lock which automatically positively holds the piston and knife in raised position for any length of time even in the absence of any pressure below the piston but which automatically unlocks upon introduction of pressure above the piston to move the knife downwardly in its cutting stroke.

The invention provides various features of construc tion and arrangement hereafter more fully described, reference being had to the accompanying drawings in which,

Fig. 1 is a front elevation of a paper cutter showing the knife and knife bar with a hydraulic cylinder and piston operatively connected thereto,

Fig. 2 is a longitudinal sectional view, on the line 2-2 of Fig. 4, showing the piston lowered or retracted and with the lock disengaged,

Fig. 3 is a fragmentary section similar to Fig. 2 but showing the piston raised or extended and the lock in engaged position,

Fig. 4 is a transverse section on the line 4-4 of Fig. 3,

Fig. 5 is a perspective view of the locking plunger, and

Fig. 6 is an enlarged fragmentary section showing the lock plunger holding mechanism.

Like reference numbers apply to like parts in all of the figures.

1 represents the frame of a paper cutter on which the knife bar 2 is hung on links 3 which give it a sweeping movement in its vertical reciprocations. The knife 4 is suitably attached to the knife bar 2 and its lower cutting edge extends below the knife bar. A table 5 is nited States Patent 0 located beneaththe knife 4 on whi'chispl'acedthegpaper to be cut.

The hydraulic cylinder 6 has itslower end pivotally connected to the frame, 1 as at 7 and the upper end of the piston rod 8 is connected to the knife bar 2 as at 9. Flexible pressure hoses 10- a-nd 1-1 communicate with passages 12 and .13 leading respectively tothe upper and lower ends of the cylinder 6. Fluid pressureiscreated by a conventional pump (not shown) and isdirected to either of the hoses 10 or 11 by: a suitable valve (not shown), the specific pump and valve structure forming no part of this invention.

Within the cylinder 6 .is areciprocal piston 14 at tached to thelower end of the. pistonrod 8. The upper end ofthe piston rod has a clevis'15 inwhichi'sav hole for the pivotal connection 9 with the knife bar 2 and the'lower end of. the cylinder 6 hastan ear havingahole for .the pivotal connectionj7 with the frame 1. The upper end of the cylinder 6 has a head .17 through which the piston rod 8 passes, andwsuitable packing 18 surrounds the piston rod-to prevent leakage of the pressure fluid.

The passage 1-3 communicates with :the lowerend. of the cylinder 6 below the piston 14 and the passage 12 leads to a lock cylinder 19 fronrwhich a port 20 communicates. with the upper end oh the cylinder, 6 above the piston. 14. The pressure fluid: will enter. or leave the cylinder through thepassages 12 and. .13 depending upon the setting of the pressure, control valve previously mentioned but not shown.

The lock cylinder 19 is formed partlyi'nthe cylinder head 17 and partly in 't-he-bosspzl. whichis .attachedto the outer side of the cylinder 6 andahas its axis-crossing the axis of the piston. rod S atright. anglesthereto. The outer end-of the lock cylinden I9, is'closedxhy. a cap 22 which has a centralvent opening23.

A lock plunger 24 is slidably mounted in the lock cylinder 19 and is provided with a relatively light spring 25 which urges the plunger toward the piston rod 8 so that the latch extension 26 on the inner end thereof will enter the annular groove 27 in the piston rod 8 when the rod is fully extended and the piston rod will thus be positively held against movement so long as the latch 26 is in the groove 27.

When the lock plunger 24 is in inner locking position it covers the port 20 between the cylinder 6 and the lock cylinder 19 so that when pressure fluid is admitted through the passage 12 and into the cylinder 19 its pressure must first move the lock plunger 24 outwardly to open the port 20 into the cylinder 6 and this outward movement of the plunger removes the latch 26 from the groove 27 in the piston rod releasing the piston 14 for downward movement.

To assure the movements of the lock plunger 24 at the proper times, a holding mechanism is provided which comprises an annular V groove 28 in the piston rod spaced from the groove 27 and a like annular V groove 29 around the body of the plunger 24. Two holding pins 30 and 31 are slidably mounted in the cylinder head 17 and the boss 21 at right angles to each other. The pin 30 is positioned to engage the piston rod 8 and to enter the groove 28 therein and the pin .31 is arranged to engage the plunger 24 and to enter its groove 29. Both ends of both pins are tapered and the: adjacent ends of the respective pins have a cam acting engagement with each other.

Operation When it is desired to raise the piston 14 from its lower position of Fig. 2 to its upper position of Fig. 3, the pressure control valve is adjusted so that pressure fluid is admitted to lower end of the cylinder 6 through the passage 13 and is released from the upper end of the cylinder through the passage 12.

During this upward movement of the piston 14 the lock plunger 24 is held outward to uncover the port by the pin 31 which is held in the groove 29 by the pin 30, the inner end of which rides against the piston rod 8. When the piston 14 reaches the upper end of its stroke, the inner end of the pin 30 may enter the groove 28 in the piston rod, releasing the pin 31 and since there is no pressure in the lock cylinder 19 the spring 25 will move the plunger 24 inwardly, pushing the pin 31 out of the groove 29 and camming the pin into the groove 28. This inward movement of the plunger 24 causes its latch extension 26 to enter the groove 27 in the piston rod thus positively holding the piston 14 in raised position and supporting any weight on the piston rod 8, such as the knife 3 and the knife bar 2, even though the pressure below the piston may decrease or entirely vanish, and this locking engagement will maintain until pressure is introduced into the lock cylinder 19 through the passage 12.

Tolower the piston from its upper position of Fig. 3, the pressure control valve is adjusted to admit pressure fluid through the passage 12 into the lock cylinder 19 and releasing the pressure below the piston through the passage 13. But since the plunger 24 is closing the port 20, the pressure will be exerted against the plunger forcing it outward, unlatching the latch 26, compressing the spring 25, opening the port 20 and aligning the groove 29 with the pin 31. Then the pressure fluid will pass through the port 20 into the cylinder 6 above the piston 14 moving it downward and at the first part of the downward movement the pin 30 will be thrust out of the groove 28 in the piston rod and will move and hold the pin 31 into the groove 29, thus holding the plunger 24 in its outward unlocked position and with the port 20 open until the piston 14 is again moved upwardly after which the operation can be completed.

This locking device is entirely automatic and will opcrate, merely by actuating the pressure control valve in the usual way, to positively hold the load lifted by the piston for any prolonged period regardless of any dimi- -nuti0n of perssure below the piston.

The invention is defined by the appended claims and is to be considered comprehensive of all forms coming within their scope.

1 claim:

1. A main cylinder, a piston in said cylinder, a piston rod attached to said piston and projecting from an end of said cylinder, a locking cylinder projecting laterally Tom said main cylinder and in communication therewith, a groove in said piston rod, a lock plunger in said locking cylinder having a projection to enter said groove in the piston rod, spring means acting to move said lock plunger toward said piston rod to enter said projection into said groove, a source of pressure fluid communicating with said locking cylinder, and acting to move said lock plunger away from said piston rod and to release the projection from the groove therein, a depression in said lock plunger, a detent acting to enter said depression and to hold said lock plunger in unlocking position when the piston rod is in other than locked position, and means actuated by movement of the piston rod for moving said detent.

2. The elements of claim 1 in which said means for moving said detent comprises a second groove in said piston rod, a pin slidably mounted to engage said piston rod or to enter said second groove therein, said pin also engaging said detent and acting to thrust said detent into said depression when the pin engages said piston rod and to release said detent when the pin enters said second groove in the piston rod.

References Cited in the file of this patent UNITED STATES PATENTS 2,130,618 Gnavi Sept. 20, 1938 2,342,812 Martinson Feb. 29, 1944 FOREIGN PATENTS 430,780 Germany June 24, 1926 

